Her team, whose findings are published in Heart, assessed the public health benefits and cost effectiveness of different strategies for reducing dietary salt content – a factor known to have a key role in the increased risk of heart disease and stroke.

They looked at the current Australian programme called 'Tick' that enables food manufacturers to buy an endorsed logo for use on product packaging to achieve higher sales in return for voluntarily reducing their salt content.

They also looked at the impact of mandatory reductions in salt content and professional advice to cut dietary salt for those at increased and high risk of cardiovascular disease.

They then costed the different strategies in terms of their impact on years of good health over a lifetime, and the associated savings in long term health care spend. And they compared the results with what would happen if none of these strategies were in place.

They took into consideration the salt content of bread, margarine, and cereals, the tonnage of product sold, average consumption per head of these products, the costs of drafting and enforcing legislation and systematic reviews of the evidence for the impact of dietary advice from health care professionals.

Their calculations showed that 610,000 years of healthy life could be gained if everyone reduced their salt intake to recommended limits of a maximum 6g a day).

But providing dietary advice to reduce salt intake is not cost effective, even if directed towards those with the highest blood pressure readings, and most at risk of cardiovascular disease. It would only cut ill health from cardiovascular disease by less than 0.5%.

The researchers said: "High blood pressure is the leading cause of mortality from cardiovascular disease. Diets high in salt have been linked to high blood pressure levels and increased risk of stroke and cardiovascular outcomes.

"Salt is a cheap ingredient for food manufacturers and is not essential at such high levels. There is no evidence of harm from small and gradual salt reductions.

"Salt is added to processed foods for many reasons; to entice further consumption, to bulk a product up cheaply by increasing water-holding capacity, or to promote drink sales by increasing thirst."